Highly Concentrated Alginate-Gellan Gum Composites for 3D Plotting of Complex Tissue Engineering Scaffolds.

Ashwini Akkineni,Tilman Ahlfeld,Anja Waske,Alexander Funk,Michael Gelinsky,Anja Lode

doi:10.3390/polym8050170

Abstract

In tissue engineering, additive manufacturing (AM) technologies have brought considerable progress as they allow the fabrication of three-dimensional (3D) structures with defined architecture. 3D plotting is a versatile, extrusion-based AM technology suitable for processing a wide range of biomaterials including hydrogels. In this study, composites of highly concentrated alginate and gellan gum were prepared in order to combine the excellent printing properties of alginate with the favorable gelling characteristics of gellan gum. Mixtures of 16.7 wt % alginate and 2 or 3 wt % gellan gum were found applicable for 3D plotting. Characterization of the resulting composite scaffolds revealed an increased stiffness in the wet state (15%–20% higher Young’s modulus) and significantly lower volume swelling in cell culture medium compared to pure alginate scaffolds (~10% vs. ~23%). Cytocompatibility experiments with human mesenchymal stem cells (hMSC) revealed that cell attachment was improved—the seeding efficiency was ~2.5–3.5 times higher on the composites than on pure alginate. Additionally, the composites were shown to support hMSC proliferation and early osteogenic differentiation. In conclusion, print fidelity of highly concentrated alginate-gellan gum composites was comparable to those of pure alginate; after plotting and crosslinking, the scaffolds possessed improved qualities regarding shape fidelity, mechanical strength, and initial cell attachment making them attractive for tissue engineering applications.

Highlights

Since the discovery of gellan gum, an anionic polysaccharide produced by the bacteriaSphingomonas paucimobilis, it has found wide spread applications in food industry as a gelling/stabilizing agent and in plant and bacterial culture systems [1,2,3,4]
We have recently demonstrated that highly concentrated pastes (16.7% alginate and alginate/gelatin blends) can be processed by 3D
Viscosity as an important parameter for 3D extrusion was studied with a rotary viscosimeter by applying a constant as well as an increasing shear rate on the pastes (Figure 1)

Summary

Introduction

Since the discovery of gellan gum, an anionic polysaccharide produced by the bacteriaSphingomonas paucimobilis, it has found wide spread applications in food industry as a gelling/stabilizing agent and in plant and bacterial culture systems [1,2,3,4]. Since the discovery of gellan gum, an anionic polysaccharide produced by the bacteria. Sphingomonas paucimobilis, it has found wide spread applications in food industry as a gelling/. Its suitability for tissue engineering approaches has been studied because of its versatile gelling properties, i.e., thermo-reversible gelling at near body temperature and ionotropic gelling by low concentrations of mono-, di- or trivalent cations. Gellan gum readily dissolves in water or aqueous solutions at higher temperatures (more than ~40 ̋ C) at which the polymer chains exist as disordered coils. When cooling down, they form ordered helical structures resulting in a weak thermo-reversible gel.

Results

Discussion

Conclusion